Americans are responding to the devastation wrought by the cyclone in Burma last week with an outpouring of support to U.S. charities and disaster relief groups, but geopolitics are complicating their efforts.

Aid workers and supplies from some U.S. nonprofit groups are not being allowed into the country, and some of those charities said yesterday that they are refusing to funnel aid through the Burmese government. Instead of directing philanthropic dollars through the ruling junta government, some charities said, they are directly assisting relief agencies on the ground in Burma.

Still, Americans are opening their wallets to help those left orphaned, hungry and homeless by the storm that hit the nation Saturday.

Save the Children, one of the largest aid groups operating in Burma, said it received $644,000 in private contributions in 24 hours and will issue a plea for $10 million.

Other U.S.-based charities launched multimillion-dollar drives to deliver rice, fresh water and plastic sheets, and students at Harvard University are selling red Burma T-shirts to raise money for victims.

"This has touched a lot of people around the world, absolutely," said Patrick McCormick, a spokesman for UNICEF, which is raising money for its emergency response. "The response has been very, very good."

Direct Relief International said it has received cash donations from thousands of Americans and has a team of doctors waiting to be dispatched from Los Angeles. But because the agency's workers have been denied visas to enter Burma, the charity is instead directing support through vetted partner organizations already there, said Brett Williams, the group's emergency response coordinator.

"The government has said they were open to charitable contributions, but they want to act as the coordinating body," Williams said. "We're not going to do that."

Although there is no official tally of the charitable response to the cyclone, philanthropy experts predicted that initial donations would be less than for some previous catastrophes.

Because the government in Burma is trying to control the charitable response, some Americans could be turned off from donating as they have after other natural catastrophes, said Patrick M. Rooney, director of research at the Center on Philanthropy at Indiana University.

"I think they will be hesitant to give money that's going directly to the junta just because of concerns about how that money will be used," Rooney said. "Is it going to help the army or to help the people?"

Some Web sites are trying to direct people to charities, such as those already in Burma, that are operating their relief efforts independently from the nation's government.

GlobalGiving.org, a leading online philanthropy marketplace, set up a fund that shepherds donations to grass-roots emergency aid projects that the organization has vetted.

The Harvard Burma Action Movement, a political advocacy group, is selling T-shirts for $20, with $14 from each sale going to cyclone survivors.

"People who haven't even heard of Burma have been buying them," said the group's incoming president, Katie Fitzgerald, 20, a junior.

The American Red Cross has been collecting donations and received $1 million from the U.S. government for its efforts in Burma. Tomorrow, the agency plans to fly in water, bed nets to try to control malaria and other supplies, said Christy Feig, a Red Cross spokeswoman.

"If we can help people get clean drinking water, you can reduce the risk of a lot of diseases," Feig said.

Relief groups in Burma received large donations yesterday and were expecting more.

Save the Children, which has operated in Burma since 1995, has 500 workers in the country and has shipped 30 tons of supplies there over the past two days, spokesman Mike Kiernan said.

"We have an ongoing relationship with local and regional authorities, and they understand what we can do," Kiernan said. "That's not to say there aren't enormous challenges in this region, which is still largely covered by water. There's a great concern about the outbreak of water-borne diseases that could increase the death toll."

World Vision, a Christian charity, has issued an appeal for $3 million to fund its work in Burma. The group has been distributing rice and water as well as tents, tarps and medicines.

"We've had plenty of people donating online and calling," spokesman Casey Calamusa said. "Obviously, people here care about it, and it's something they want to act on."